Rockwell Automation 22-SCM-232 Serial Converter Module - Manual (Page 95)

Glossary
A
Application Code
Code that runs in the serial converter module after the boot code calls it.
It performs the normal operations of the system.
B
BCC
Block Check Character. An error detection scheme where the 2’s
complement of the 8-bit sum (modulo-256 arithmetic sum) of all data
bytes in a transmission block. It provides a means of checking the
accuracy of each message transmission.
Boot Code
Code that runs when the serial converter module first receives power. It
checks basic operations and then calls the application code.
C
CRC
Cyclic redundancy check. An error detection scheme where all of the
characters in a message are treated as a string of bits representing a
binary number. This number is divided by a predetermined binary
number (a polynomial) and the remainder is appended to the message as
a CRC character. A similar operation occurs at the receiving end to prove
transmission integrity.
D
DF1 Protocol
A peer-to-peer link layer protocol that combines features of ANSI
X3.28-1976 specification subcategories D1 (data transparency) and F1
(two-way simultaneous transmission with embedded responses).
DF1 Rate
A unit of signaling speed equal to the number of discrete conditions or
signal events per second. It is also called “baud rate” or “serial port rate.”
DSI
Drive Serial Interface - a modification of the ModBus RS-485 serial
communications protocol used by various Allen-Bradley drives and
power products.
DSI Peripheral
A device that provides an interface between DSI and a network or user.
Peripheral devices are also referred to as “adapters” and “modules.” The